1. Field of the Invention
The present invention relates to a novel linear wind powered electric generator (LWPEG), which is particularly adapted for installation at geographical sites subject to lower wind intensities. More specifically, the invention is directed to the provision of a track based design concept for an LWPEG, possessing reasonable economic parameters for utilization at the lower-intensity wind sites. Moreover, the linear wind powered electric generator is based on a track based wind power generator, incorporating aerodynamic designs, which are adapted to reduce mechanical complexities presently encountered in this technology, while being cost-effective both in construction and in connection with the operation thereof.
The concept of windmills has been proposed over a considerable period of time for harnessing the power of the wind, in the form of wind turbines generating electrical energy. Wind power provides a plentiful, renewable, geographically widely distributed, clean source of energy, while concurrently ameliorating the danger of generating deleterious by-products and greenhouse gas emissions, by replacing fossil fuel-derived electricity.
Wind energy, which is similar to solar energy in representing a clean form of renewable energy, can be exploited for generating viable electrical power and is becoming more and more economically and environmentally relevant. In this technology, there are currently known many diverse essentially conventional axis-based windmill or turbine designs operating with horizontal (wind) axes, and others functioning with vertical (cross) axes.
Measured on a worldwide scale, the geographically available wind energy resources are immense, and are potentially capable of satisfying all current energy needs of mankind several times over. However, unfortunately, wind energy is not available universally in equal wind intensities. Based upon so-called energy density, wind intensities are classified into seven general classes, with the 7th class being identified as being the strongest and the 1st class as being the weakest. Thus, wind density in a country, for example, such as India, is very poor compared with that available, for instance, in North America and Northern Europe, wherein all current wind turbine designs are rated for a Class 6 wind density, which was defined as a reference wind regime by the United States of America in the mid-1980s. In this connection, the annual energy available for the Class 6 wind density is about 5200 kWh/year/m2, and reduces for a Class 2 wind density to about 1200 kWh/year/m2 at a height of 50 m above ground level.
Generally, large expanses in area have been identified as Class 2 wind sites, i.e., possessing a wind power density of 1200 kWh/year/m2 at 50 m above ground levels. Thus, for example, official data for India alone indicates that nearly 89% of installable wind power capacity here is at the low Class 2 wind density. Horizontal axis wind turbine (HAWT) technology, as presently employed, is deemed inappropriate for Class 2 wind density sites. Consequently, in order for low wind energy having to significantly contribute within the next or future decades, installations imbued with good operating economics under Class 2 wind density conditions are required. Such installations must afford a substantially higher annual energy extraction under prevailing annual wind velocity distributions when compared to HAWTs, such as the linear wind powered electric generator (LWPEG) contemplated by the present invention.
Pursuant to the current state of the art, over 95% of current wind turbine designs are three-bladed or two-propeller-type horizontal axis wind turbines (HAWT) whereas vertical axis wind turbines (VAWT) are normally considered for stand-alone units possessing low power ratings, whereby also a few multi-bladed HAWT and split-drum type VAWTs are employed for water pumping purposes. Over 25 years ago, as mentioned, the United States Department of Energy and NASA defined Class 6 wind density as the reference wind regime for the United States, which is geographically close to the average wind resource of the United States. Currently, all major wind turbine manufacturers base their designs on Class 6 wind densities, which are slated to operate under Class 6 to Class 7 wind ranges. Special efforts have been made somewhat more recently to develop the so-called ‘Low Speed Wind Technology’, as referred to in Class 4 wind density whereby, in fact, winds of Class 3 and above are considered as an energy resource. Consequently, at this time, there are no competitive technological solutions available for Class 2 wind resources, with major wind turbine manufacturers, who developed their designs for Class 6 wind resources, making an attempt to market the designs for low-wind sites by either increasing the wind turbine hub height and rotor diameter at a higher cost, or by de-rating the design, again at a higher cost for energy.
Most of the presently installed wind turbine power, for example, in countries like India, is in HAWT designs and occupies Class 3 to Class 5 wind sites. However, it is noted that only about 10% of the wind energy potential is available in these wind intensity classes, with the remainder being in Class 2.The total wind energy potential in Class 3 to 5 winds adds up to about 5000 MW. Thus, if wind energy is to contribute substantially to power generation within the next decades, then it becomes necessary to be able to develop power generating designs with reasonable economic parameters for Class 2 wind sites.
2. The Prior Art
Although numerous windmills in the form of power-generating wind turbines are currently known, and are widely installed and operated at numerous sites in different countries and locales, these are primarily prevalent of the designs which are required for high-density wind applications, i.e., significantly higher than for Class 2 wind sites.
Thus, among publications of interest there may be considered the disclosures of U.S. Pat. No. 4,218,183, U.S. Pat. No. 7,360,995; U.S. Patent Publication No. 2004/164562; U.S. Pat. No. 4,302,684; U.S. Patent Publication No. 2004/080166; U.S. Pat. No. 6,672,522 B2; U.S. Pat. No. 5,758,911; U.S. Pat. No. 4,114,046 and U.S. Pat. No. 5,730,643.
There are represented two primary types of wind turbines, i.e., the widely employed horizontal axis wind turbine (HAWT) designs, and the somewhat less used vertical axis wind turbine (VAWT) design, whereby the horizontal axis wind turbine (HAWT) technology is clearly deemed to be inappropriate for Class 2 wind sites. Thus, installations with good operating economics under low-velocity winds, and which provide substantially higher annual energy extraction levels under local prevailing annual wind velocity distributions, when compared with presently available HAWTs and other designs must be developed.
In the above referenced prior art publications, there are disclosures which are concerned with vertical and horizontal axis wind power generating systems, as well as track-based, pulley-guided wind power generating systems with different complex combination of mechanical components, such as sails or the like, or which utilize earlier technologies that do not translate well into modern economies of scale. Further, the existing design concepts of wind power generating systems are only adapted for operation with higher-density classes of winds, and as such, are not readily capable of being utilized successfully, especially on commercial scales, for the low density Class 2 wind sites.